This invention relates to winding apparatus for winding tapes, cords and so on onto cores mounted on a drive shaft.
An air differential shaft differs from other types of mandrels that are designed to lock a core to the mandrel to prevent rotational slip between the core and the mandrel. Rotational slip is provided between the core and the mandrel to allow the mandrel to rewind multiple rolls on a single shaft at the same time. In a lock core mandrel no rotational slip is present between the drive mechanism and the core. A plurality of cores are mounted on a common shaft, each core for forming a separate roll. If all of the cores mounted on a common shaft are not the same inner diameter due to caliper variations, the smaller diameter rolls lose tension. This is undesirable as all rolls need uniform tension to uniformly wind the tapes, cords etc. onto the cores.
If the tension is too low, the elongated members may be wound too loosely. If the tension gets too high, the elongated member may break. Either condition is not acceptable on a high speed mass production apparatus.
The slip mandrels fall into two broad categories, xe2x80x9cdirect frictionxe2x80x9d or xe2x80x9cslip ringxe2x80x9d type. In the direct friction type, the slipping xe2x80x9cclutch facexe2x80x9d is between the core and the outside diameter of the mandrel. The slip ring type has a separate ring where the slipping takes place between the ring and the mandrel.
The slip ring works by stacking them axially in an array on a hollow tube called a body. A series of holes are bored into the body that allow pistons in the holes to protrude against an inner ring having outer ramp channels receiving balls mounted radially in the slip ring. A bladder inside the body is expanded by air pressure to force the pistons into the inner ring. The slip ring is external the inner ring and the balls protrude radially outwardly therefrom. The pistons when forced against the inner ring produces friction with the inner ring. The rotating body rotates the pistons therewith which in turn torque the inner ring rotating it. The rotating inner ring radially inclined ramp channels are intended to cause the balls to ride up the corresponding ramps. This ramping action displaces the balls radially outwardly into the hard paperboard core to grip it. This is intended to rotate the core.
However, this mechanism experiences problems. The balls initially are not sufficiently frictionally engaged with the core. When the pistons are activated not all of the balls engage their corresponding cores with uniform friction so that some cores may not rotate or rotate at different speeds than other cores. The slip rings and outer rings may rotate in unison so that the clutch action of the slip rings and balls is not activated. There must be relative rotation of the slip ring to the outer ring. The present inventor has discovered that the cause of this problem is that there is insufficient friction between the outer ring and core. Thus when the pistons engage the different the inner rings to rotate the inner rings, the outer rings will rotate with the inner rings and the clutch action does not operate. That is, when the outer ring rotates relative to the inner ring, the clutch balls ride up the ramp of the inner ring and grip the core. If there is no relative rotation the ramp action does not occur and the balls do not grip the core. This results in not driving the various cores with a uniform torque, causing uneven winding on the different cores.
The problem of inconsistent slip ring tension is addressed in U.S. Pat. No. 5,451,010 which discloses friction elements that pivot outwardly to provide initial drag so that the core can be held by the piston action. This is relatively complex and costly. The friction elements protrude and do not facilitate core removal. The core needs to be rotated to remove it from the mandrel requiring additional work by an operator.
In U.S. Pat. No. 4,026,488 to Hashimoto, cylindrical winding cores are mounted on a plurality core holders and a plurality of friction collars are mounted alternately on a single hollow shaft under axial pressure. Each of the collars is allowed to be axially moved and constrained in rotation and each of the core holders has a radial expansible means which are radially expanded by an air pressure supplied to a hollow shaft to come into pressure engagement with the inner surfaces of the cylindrical winding cores on the core holders. Catch buttons are used with a leaf spring to return the catch button to its retracted position when pressure is lost. When pressure is applied to a pressure chamber, the leaf spring and expansible means cooperate to push the catch buttons outwardly to grip a core. The expansible means is a radially expansible elastic half tube and responsive to pneumatic pressure applied to a pressure chamber. Pressure is applied axially to couple the T-shaped collars for rotation which pressure is changed to change the magnitude of the axial pressure applied from a shaft end. This is a relatively complex and costly apparatus.
In U.S Pat. No. 2,215,069, spindles are disclosed for rolls to be wound on cores with a uniform grip. Disclosed plugs may be thrust outwardly into engagement with a core by means of a pressurized air inflatable tube encircling an inner shell and bound thereto by bands. When the tube is inflated the plugs are pressed outwardly and apply a pressure against the core inner wall to provide a compact winding and uniform tension.
U.S Pat. No. 2,849,192 to Fairchild discloses a core engaging shaft. Fluid pressure is applied to a diaphragm and bulge it outwardly to grip a core.
U.S Pat. No. 3,006,152 to Rusche discloses a pile driving mandrel.
U.S Pat. No. 3,053,467 to Gidge discloses an expansible shaft employing fluid pressure. Self retractable gripping elastomeric members are mounted along an inner face of an outer shell, each with a radially extending portion. The shell is rigid and perforated with radial passages each receiving a member radial portion. Pressure deforms the members radially outwardly in the passages and project beyond the shell to increase the overall diameter of the shell. An inner inflatable container forms an elongated chamber with the inner face of the shell. The container is inflated to distort the buttons and cause the buttons to extend from the shell.
U.S Pat. Nos. 3,127,124, 4,220,291, 4,332,356, 4,953,877 and 6,079,662 disclose chucks and apparatus related to winding tape and similar products on cores. Many of the above patents relate generally to providing plugs which radially extend outwardly for gripping a core. The problem as recognized by the present inventor with these apparatuses is that while the plugs are intended to provide uniform tension on the strips, tapes and so on being wound by gripping the cores with the plugs, there is still present a problem of lack of uniform tension on the strips and so on in many instances. Such lack of uniform tension may result in breakage or loose windings as discussed above. Further, none of these patents address the slip ring problem employing ramp type inner rings coupled with pistons and balls as discussed above.
A ring assembly according to the present invention is for mounting a core upon which an elongated element is to be wound, the ring assembly being driven by a drive shaft about an axis, the shaft including radially outwardly displaceable pistons for coupling the ring assembly to the core. The assembly comprises an outer ring member for releasably mounting a first core thereon and having a plurality of annularly spaced radial first and second bores. A first core gripping member is movable in each of the first bores and has a first position recessed in the first bore and a second position protruding radially outwardly from the first bore for gripping the core. A second core gripping member is movable in each of the second bores, the second gripping member having a third position recessed in the second bore and a fourth position protruding radially outwardly from the second bore for gripping the core. A resilient member is in the second bore for normally biasing the second core gripping member radially outwardly to the fourth position. An inner ring member is radially within the outer ring member, the inner ring member having an inner annular surface for facing the shaft and for engagement with the pistons and an outer ramped annular surface facing the outer ring member extending about the axis and sloping radially outwardly for engagement with and displacing the first gripping member radially outwardly to the second position upon relative rotation of the inner ring member about the axis with respect to the outer ring member in response to the radial outward displacement of the pistons.
In one aspect, the ramped annular surface comprises a groove semi-circular in transverse section.
In a further aspect, there are a plurality of ramped annular surfaces each extending about the ring member equal amounts to subtend equal chords.
In a further aspect, the first and second core gripping members are balls. The first gripping members preferably are larger diameter than the second gripping members. Preferably, the resilient member is a compression spring.
In a further aspect, the inner ring is molded thermoset plastic material.
The first bores preferably alternate circumferentially with the second bores about the outer ring member. Preferably there are four first bores and four second bores and preferably the first bores area bout 30% larger in diameter than the second bores.